Open Engine Lid at Hinge

On friends XJ we did a test on air flow with the hinge side of the engine lid propped open by one inch high spacers at the hinges. We place three streamers along the propped open edge of lid, and then drove. At highway speeds the streamers showed flow going into the engine bay. This may well result in less airflow thru the radiator. It certainly did not improve highway cooling. Suspect high pressure at the base of windshield causes this air flow pattern.

They sell kits for that, don't know if they really work, they might be better at slow speeds were it's needed.

Auto engineers (and aeronautical engineers) have developed cowl induction setups to benefit engine performance by using this high-pressure area to introduce cooler fresh air into the intake. Think 1970 Chevelle Cowl Induction hood.
The THOR XJ cowl intake setup is a variant.

The XJ platform will benefit from better dissipation of engine heat by placing hood vents where the air can pass through the radiator and escape up and out of the engine compartment in the low pressure area, which means placing the vents closer to the front of the hood and not near the windshield. You see this on race cars, super cars, 5.9 ZJ hoods, my hood.....etc.




NOTE: The addition of hood vents will not solve a cooling problem, but it MAY help your XJ run cooler and reduce the potential for heatsoak.

XJEEPER said:

Auto engineers (and aeronautical engineers) have developed cowl induction setups to benefit engine performance by using this high-pressure area to introduce cooler fresh air into the intake. Think 1970 Chevelle Cowl Induction hood.
The THOR XJ cowl intake setup is a variant.

The XJ platform will benefit from better dissipation of engine heat by placing hood vents where the air can pass through the radiator and escape up and out of the engine compartment in the low pressure area, which means placing the vents closer to the front of the hood and not near the windshield. You see this on race cars, super cars, 5.9 ZJ hoods, my hood.....etc.

NOTE: The addition of hood vents will not solve a cooling problem, but it MAY help your XJ run cooler and reduce the potential for heatsoak.

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I am in agreement 100%. The low pressure at the front of the hood is the best location for heat venting when at highway speeds. While we are at it, Where did you get those vents? I keep hoping to come across some vents that fit exactly where those are placed but have no luck.

techno1154 said:

I am in agreement 100%. The low pressure at the front of the hood is the best location for heat venting when at highway speeds. While we are at it, Where did you get those vents? I keep hoping to come across some vents that fit exactly where those are placed but have no luck.

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I did almost the exact same thing with these:

http://rodlouvers.com/Pair-of-Angled-11-Louvered-panels-4-P1036801.aspx

The angle on them is almost perfect for the XJ to install along the edges of the crease in the hood. The louvers end up almost exactly parallel on the hood with them angled outwards. After install, almost everything works better: AC, less fan time to keep it cool, less heat soak, etc.

Tuft test says they work decently at highway speeds. Not perfect like you'd see on a racecar, but there's definitely outflow.

BTW, I painted mine with black trim and bumper paint, rounded the corners with a flap disc, and used stainless button-head machine screws and washers for a clean look.

techno1154 said:

I am in agreement 100%. The low pressure at the front of the hood is the best location for heat venting when at highway speeds. While we are at it, Where did you get those vents? I keep hoping to come across some vents that fit exactly where those are placed but have no luck.

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These vents are GenRight Offroad units.

XJEEPER said:

These vents are GenRight Offroad units.

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https://genright.com/products/hood-louver-set-2pc-long-black.html

XJEEPER said:

https://genright.com/products/hood-louver-set-2pc-long-black.html

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Thank you.

They look really nice,....exactly what I have been looking for. I will be getting a set of them.

I'm sure you've seen the hoods with the scoop facing the window, they're called cowl induction because the would pull in the air here and go right to the air cleaner back when they sat atop the carb.

Scott91370 said:

I'm sure you've seen the hoods with the scoop facing the window, they're called cowl induction because the would pull in the air here and go right to the air cleaner back when they sat atop the carb.

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Yea! That is right,...cowl induction,... (ram air)they usually face forward and sealed around the engine intake port,...carburetor come to mind. As far as I know, they did nothing to help with the engine room cooling.

Most XJ vents are to facilitate engine room cooling, including various wranglers throughout the years.